Intersubband transitions in Al0.82In0.18N/GaN single quantum well

The influence of the width of a lattice-matched Al_0.82In_0.18N/GaN single quantum well (SQW) on the absorption coefficients and wavelength of the intersubband transition (ISBT) has been investigated by solving the Schrödinger and Poisson equations self-consistently. The wavelength of 1—2 ISBT increases with L, the thickness of the single quantum well, ranging from 2.88 μm to 3.59 μm. The absorption coefficients of 1—2 ISBT increase with L at first and then decrease with L, with a maximum when L is equal to 2.6 nm. The wavelength of 1—3 ISBT decreases with L at first and then increases with L, with a minimum when L is equal to 4 nm, ranging from approximately 2.03 μm to near 2.11 μm. The absorption coefficients of 1—3 ISBT decrease with L. The results indicate that mid-infrared can be realized by the Al_0.82In_0.18N/GaN SQW. In addition, the wavelength and absorption coefficients of ISBT can be adjusted by changing the width of the SQW.     

大孔径双向聚能射孔弹的研究

 设计了一种双锥药型罩与双向装药结构相结合的聚能射孔弹模型,通过数值模拟方法研究其射流成型机理,并计算其射流参数。结果显示：双锥药型罩的小锥角部分形成聚能射流,大锥角部分形成翻转弹丸,射流头部和弹丸的速度分别为6 250 m/s和1 620.9 m/s,弹丸长度和平均直径分别为26.1 mm和8.6 mm。结合数值模拟结果,对射流侵彻公式进行了修正,并利用修正公式预测该射孔弹侵彻钢靶的深度,计算结果为69.6 mm。最后,按照该模型进行侵彻实验,实验回收弹丸的长度和平均直径分别为28.1 mm和8.8 mm,侵彻钢靶的深度和孔径分别为70 mm和17 mm。实验表明：数值模拟与理论计算方法相结合是可行的,能够有效地计算射孔弹的射流参数并预测其侵彻深度;该射孔弹侵彻性能优越。     

大学物理双语教学的实践与思考

介绍了大连海事大学航海类专业大学物理双语教学的实践,探讨了大学物理教学中开展双语教学的模式,总结了教学过程中的经验和体会.     

A Monte Carlo study for the shielding of γ backgrounds induced by radionuclides for CDEX

The CDEX (China Dark matter EXperiment) Collaboration will carry out a direct search for WIMPs (Weakly Interacting Massive Particles) using an Ultra-Low Energy Threshold High Purity Germanium (ULE-HPGe) detector at the CJPL (China JinPing deep underground Laboratory). A complex shielding system was designed to reduce backgrounds and a detailed GEANT4 Monte Carlo simulation was performed to study the achievable reduction of γ rays induced by radionuclides and neutron backgrounds by D(γ,n)p reaction. Furthermore, the upper level of allowed radiopurity of shielding materials was estimated under the constraint of the expected goal. Compared with the radiopurity reported by other low-background rare-event experiments, it indicates that the shielding used in the CDEX can be made out of materials with obtainable radiopurity.     

纳米结构Au/Fe_2O_3的制备、表征及催化氧化性能

分别以纳米和块状氧化铁为载体,通过沉积沉淀法制备了Au/Nano-Fe2O3和Au/Bulk-Fe2O3,并对其进行了表征和催化氧化性能测试。结果表明:对于Au/Nano-Fe2O3,5 nm Au颗粒被尺寸相当的Nano-Fe2O3所包覆,形成新颖的类似核壳结构;对于Au/Bulk-Fe2O3,3 nm Au颗粒高度分散于Bulk-Fe2O3的表面。在1-苯乙醇的氧化反应中,Au/Nano-Fe2O3显示出比Au/Bulk-Fe2O3更好的催化活性。活性的增强主要与小尺寸的Nano-Fe2O3以及Au和Nano-Fe2O3更大的接触界面有关。相比于广泛受到重视的Au的尺寸效应来说,对于Au/Nano-Fe2O3而言,Fe2O3尺寸的影响更大。     

新型辐射变色凝胶的紫外辐照研究

将类丁二炔化合物自组装成纳米囊泡后,均匀分散于凝胶载体中,研制出一种新型的辐射变色凝胶剂量计。用电镜观测了囊泡形貌,采用CL-1000型紫外交联仪对凝胶进行辐照,测试并研究了凝胶对紫外辐照的变色响应、辐射后效应、扩散效应等剂量学性能。结果表明:该辐射变色凝胶在5~150mJ/cm2能量密度范围内对紫外线辐照具有良好的响应线性,同时克服了扩散效应、辐射后效应、成型能力差等现有凝胶剂量计的不足。该辐射变色凝胶剂量计适于光学扫描方式测量剂量分布。     

Fast parallel algorithm for three-dimensional distance-driven model in iterative computed tomography reconstruction

The projection matrix model is used to describe the physical relationship between reconstructed object and projection.Such a model has a strong influence on projection and backprojection,two vital operations in iterative computed tomographic reconstruction.The distance-driven model(DDM) is a state-of-the-art technology that simulates forward and back projections.This model has a low computational complexity and a relatively high spatial resolution;however,it includes only a few methods in a parallel operation with a matched model scheme.This study introduces a fast and parallelizable algorithm to improve the traditional DDM for computing the parallel projection and backprojection operations.Our proposed model has been implemented on a GPU(graphic processing unit) platform and has achieved satisfactory computational efficiency with no approximation.The runtime for the projection and backprojection operations with our model is approximately 4.5 s and 10.5 s per loop,respectively,with an image size of 256×256×256 and 360 projections with a size of 512×512.We compare several general algorithms that have been proposed for maximizing GPU efficiency by using the unmatched projection/backprojection models in a parallel computation.The imaging resolution is not sacrificed and remains accurate during computed tomographic reconstruction.     

Structure of the even-even ~(78-84)Kr isotopes within SD-pair shell model

The collective properties in the even-even 78-84Kr isotopes have been studied within the framework of the SD-pair shell model.It is found that the collectivity of low-lying states in the even-even Kr isotopes can be described very well.     

指纹紫外光谱特性研究及变化规律分析

指纹的唯一性和终身不变性使得指纹可以验证一个人的身份信息,在生物识别领域具有广泛的应用。汗潜指纹对紫外线有着特殊的反射、散射以及荧光特性,所以可以利用紫外波段对汗潜指纹进行提取,并且不污染现场和目标样本。目前对紫外波段的指纹提取已经有着广泛的研究,但对指纹随时间变化的研究较少,一般都是通过化学方法测量汗潜指纹成份含量的变化。研究发现,指纹各个组成成份的紫外光谱特性不同,且这些成份随时间的挥发程度也不一致,利用多通道紫外成像系统对汗潜指纹进行凝视成像,发现各通道成像DN值随时间推移的变化程度并不一样,可通过研究各通道DN值的变化对指纹进行时间分析。首先,利用紫外光谱仪和氙灯,对汗液、酒精、食用油等几种手指容易接触的物质的反射光谱进行研究,得到了这些物质的反射光谱特性。然后,针对这几种类型的指纹,研制了一套多通道紫外成像设备,分别在240~280 nm（通道1）、280~315 nm（通道2）以及315~340 nm（通道3）三个紫外通道对其进行凝视成像,得到清晰的指纹图像,将指纹图像嵴线上码值最高的10个点的平均值进行比较,得到不同通道DN值与时间变化的关系。实验结果发现,汗潜指纹在紫外波段具有良好的成像特性,其成像DN值随时间的推移逐渐降低,其中240~280 nm的通道1中三个指纹在第七天的成像DN值分别降为第一天的0.62, 0.60和0.59;320~340 nm的通道2中三个指纹在第七天的成像DN值分别降为第一天的0.57, 0.61和0.60;340~420 nm的通道3中三个指纹在第七天的成像DN值分别降为第一天的0.56, 0.63和0.58。实验结果表明,不同类型的指纹在紫外波段的光谱特性并不一致,成像DN并不相同,且随时间的变化规律也不一样,但指纹成份的挥发具有一定的规律,成像DN值从第一天到第七天降低至60%左右,可以一定程度上反映指纹的挥发性质。结合紫外多通道成像系统,可以很好的研究指纹的变化规律,为刑侦探测中指纹研究提供了一个重要的手段。     

Determining Nuclear Form factor for Detection of Dark Matter in Relativistic Mean Field Theory

In this work, we derive the nuclear form factor for the spin-independent collision between the WIMPs and nucleus in terms of the relativistic mean field (RMF) theory. Comparison with the traditional form factors which are commonly used in literature is given and it is found that our results are slightly above that of the 2PF model by 4% to 8%, but deviate from the Helm form factor by 15% to 25% for the whole recoil energy spectrum of 0 ∽ 100keV. Moreover, taking Xe and Ge as examples, we show the dependenceof the form factor on the recoil energy.